While your initial question is almost impossible to answer, I'm hoping that my response, in addition to everything sdeeer has said, will at least shed some light onto the subject.
The body "prefers" to use certain sources as primary sources for energy. We're always burning carbs, fat, and even a tiny bit of protein at the same time simply because of our metabolism, but the ratio of carbs consumed in comparison to the other sources is much much higher. Once carbs are depleted, the primary source moves to fat, and after that, protein.
So isn't it as simple as eating fat and carbs to fuel exercise and recovery, and protien for growth?
Yes, but you're confusing two concepts. Growth and recovery are more or less in the same category when it comes to the use of nutrients. You never want to consider eating fat as fuel, but more as an essential nutrient to stay healthy. Your body needs certain fats (Omega-3 Fatty Acids and all that good stuff), but that's a different subject.
Carbohydrates = Fuel
Protein = Recovery AND Growth
After a long ride, you're generally low on glycogen, and ingesting carbohydrates allows you to refill that supply. Think of it more as refilling the gas tank rather than recovering.
When you exercise, you experience DOMS: Delayed Onset Muscle Soreness. This is theorized to be caused by two major concepts: Microtrauma and Oxidative stress. Microtrauma is basically exactly what the name says. Microscopic amounts of trauma, called microtears, in the muscle tissues. Oxidative stress causes damage to the muscle due to higher oxygen consumption resulting in electron transfers. It's believed that the soreness is actually due to the rebuilding and hypertrophy of muscles rather than the actual damage. Rebuilding and hypertrophy is primarily fueled by protein. Certain types of muscle (slow-twitch vs fast-twitch) are more prone to the different types of damage.
If you deduct a little of the fat and carbs would the body use stored fat as fuel for exercise and recovery, leaving you with a loss of fat and a gain of muscle?
Yes for exercise, not so much for recovery. Like I said before, when you've depleted your carbohydrate energy, you move onto stored fat as a primary energy source. This is where most athletes "bonk." They have no readily accessible energy, so their bodies have to use fat, which is a far less efficient process. People trying to lose weight are generally consuming less carbohydrates so they enter this state faster and burn more fat. A high protein intake can help to offset muscle loss and even promote gaining lean body mass. It's difficult, but can be accomplished with the right diet and exercise program. With a low protein intake, it takes longer for you to recover since the entire recovery and growth phase is pretty much fueled solely by protein. However, an increase in muscle mass also increases the amount of calories you burn at rest, which can lead to more fat loss.
That's probably more information than you wanted, but whatever. Hope it helps.
